Jeff Steinberg's backyard oasis has a luxury pool with a walk-in beach,
an integrated hot tub and a stream with local river rocks. But there's
something it doesn't have: chlorine.

His natural swimming pool in Princeton, N.J.,
uses plants in an adjacent area to clean the water, creating an aquatic
habitat that includes water lilies, lotuses and toads.

"We
hear them croak as they dive for cover," Steinberg says, noting how the
toads scurry to their home base among the plants when his wife, Julia,
swims morning laps.

Such pools or swimming
ponds, which started gaining popularity in Austria in the 1980s and then
spread to other countries, are slowly making inroads in the United States.
At least two dozen homes now have them, according to interviews with
pool company executives, and Minneapolis officials say their city will
soon be the first in the USA with a public natural pool.

Looks 'more like a lake'

"It
won't look like a traditional pool. It will look more like a lake,"
says Cliff Swenson, project manager for the city's Webber Park, where
the swimming hole is slated to open as early as August 2013. He says it
will meet the water-quality standards for lakes, not pools - a
difference that required the state legislature to approve it as a pilot
project. Still, this is a man-made facility that will function as a
pool.

He says public health officials were hesitant,
because it won't be a sterile environment. Yet he says similar venues
in Europe haven't had bacteria problems, and the city will test the
water two to three times a week. If a problem occurs, it will close the
pool - as it does with others - and the water will be recirculated
through the wetlands and retested prior to reopening.

Swenson
says the project, which is expected to cost the same as a regular pool
to build but less to operate, reflects the city's commitment to using
sustainable measures to lower overall costs.

Similar
ones will likely follow, says James Robyn, chief executive officer of
BioNova USA, a company based in Hackettstown, N.J., that designs and
builds natural swimming pools, including the Minneapolis one.

"The biggest motivating factor is that the pool is chlorine-free," Robyn says, citing a 2011 study by the U.S.
Centers for Disease Control and Prevention that estimates that 28,071
injuries or illnesses - mostly minor respiratory, eye and skin problems -
were caused by pool chemicals between 2002 and 2008. Chlorine, a skin
irritant, has been shown to aggravate asthma.

"Clients like the fact it's a green product," he says.

"I have sensitive eyes, and it's really nice not to swim in chlorine," says John McDermott, who had a BioNova pool - finished this spring - built at his home in Nantucket, Mass.

Dive in to green water?

Chris
Paquette, co-owner of Robin's Nest Aquatics in Hollis, Maine, sees
great potential for the natural approach in homes but, citing strict
U.S. water-quality standards, not in public projects.

The
idea didn't fly in St. Paul - twin city of Minneapolis - when it was
proposed a few years ago. "The key factor was timeline," says Michael
Hahm, director of St. Paul Parks and Recreation. He says the city
didn't have the time or money to wait for the legislative or code
changes that would have likely been needed.

Another
potential obstacle is water color. "I don't know many Americans who
want green water," Paquette says, adding that algae can be a nuisance in
the first three years of a swim pond, when the plants aren't mature
enough to control it. He says ultraviolet sterilizers can help, but they
add cost.

Some guests who have stayed at Au
Cabaret Vert, a small eco-resort in Battambang, Cambodia, have
complained about the greenish water and the handful of fish in its
natural swimming pool. Others, in reviews on the travel website
TripAdvisor.com, relish the natural experience.

"This
is very sweet for your skin, and you can open your eyes under the
water," says co-owner Mathieu Damperon, a native of France who got the
idea from Germany.

The benefits have won over many foreigners. Michael Littleton, a British landscape designer and author of Natural Swimming Pools, says thousands of these pools - public and private - have been built in Europe since the 1980s and at least 100 in the United Kingdom since 2000. He says they blend well into the outdoors, often doubling as water gardens.

Steinberg
says his family spends a lot of time in and around their natural pool,
which has ultraviolet sterilizers and ozone generation to keep the
water clear. His 14-year-old daughter picked a conventional diving
board rather than the large rock that BioNova suggested.

"It's really been an outdoor room," he says. "We're looking forward to skating on it when we finally get a hard freeze."